An anal fissure is a cut or tear in the lining of the anus. The anus is the opening through which stool leaves the body. Tears generally occur just inside the opening.

Anal Fissure
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The exact cause of an anal fissure is unknown. In most cases, tearing is the result of trauma to the anal lining. Trauma can be caused by:

  • A large, dry, or hard stool
  • Frequent diarrhea
  • Tightened anal sphincter, a group of muscles that open and close the anus
  • Childbirth
  • Anal irritation